The invention relates to a method and a device for computer-based determination of a total fingerprint template from a plurality of partial fingerprint templates and a computer readable medium.
In order to provide an identification mechanism based on biometric characteristics of a person which is to be identified. One biometric characteristic often used for personal verification/identification is the person's fingerprint.
In this kind of verification/identification, typically the person's fingerprint is detected by a fingerprint sensor, thereby generating a fingerprint image.
The word “fingerprint” is herein used as a representative of a fingerprint or a like pattern or figure. More particularly, the fingerprint may be an actual finger, a palm print, a toe print, a soleprint, a squamous pattern, and a streaked pattern composed of streaks. The fingerprint may also be a diagram drawn by a skilled person to represent a faint fingerprint remain which is, for example, left at the scene of a crime.
Usually, the person, who would like to use a device for this kind of verification/identification is required to register his or her fingerprint in a registration step for later verification/identification in a verification/identification step.
During the registration, characteristic features of the fingerprint will be extracted and stored in a storage media of the device. Such a fingerprint image is called the template fingerprint and such a stored characteristic features are called the template minutiae.
When a person wants to use the device, he has to present his fingerprint to the device.
The unknown fingerprint of the person who wants to be identified in a verification/identification step is usually detected by a fingerprint sensor. The characteristic features of the detected fingerprint will be extracted and matched against the template minutae of the template fingerprint. If a match is found, the person is identified as the person the respective pre-stored template fingerprint refers to. Otherwise, the person is identified as an unauthorized user and the further use of the device will be prohibited.
The template minutiae usually comprise geometrical and other useful characteristic information (or features) pertaining to the local discontinuities (the minutiae) of the fingerprint, such as                the type of the current minutiae,        the location of the current minutiae,        the direction of the current minutiae,        the ridge count between the current minutiae and its neighboring minutiae,        the location of the neighboring minutiae,        the distance relationship of the current minutiae with respect to its neighboring minutiae, and/or        the angular relationship of the current minutiae with respect to its neighboring minutiae.        
In [1] and [2], methods to determine the template minutiae are described. The basic concept of these both methods is to determine all the minutiae present in the fingerprint image.
From these determined minutiae, the required parameters are subsequently determined.
Furthermore, methods to match the fingerprints or to compare whether two fingerprints are similar to each other or not using the fingerprint templates, are described in [3], [4], [5], or [6].
In the Singapore patent application [6], a two-stage local and global fingerprint matching technique for automated fingerprint identification is described, which disclosure is herewith entirely incorporated by reference.
Known optical fingerprint sensors usually have an imaging area of about 25.4 mm by 25.4 mm, which is usually sufficient to cover the entire surface of the finger when the finger is pressed on the imaging area of the optical fingerprint sensor. However, a typical solid-state fingerprint sensor, such as the FPS 110 sensor from Veridicom, Inc. or the FingerTip™ sensor from Infineon, Inc. has a smaller sensor area in order to ensure that the cost of the sensor is acceptably low. For example, the FPS 110 has a sensor area of 15 mm by 15 mm and the FingerTip™ sensor has a sensor area of 11.1 mm by 14.3 mm. Thus, with such a small sensor area, it is usually not possible to detect the entire fingerprint with one detection iteration, i.e. with one fingerprint image, since the sensor area is not sufficient to cover the entire surface of the finger when the finger is pressed on the sensor area of the solid-state fingerprint sensor.
This situation creates several problems such as:                How to detect and represent the entire fingerprint image (total fingerprint image) using the small sensor area?        How to make the fingerprint template determined from a detected fingerprint image using a small sensor area to be compatible to that detected by a fingerprint sensor with a larger sensor area?        How to make the fingerprint template determined from the various fingerprint images with various sizes to be compatible for fingerprint matching.        
A method to solve the above mentioned problems would be to enroll multiple fingerprints detected from the same finger but at different locations. However, this would mean that more storage space would be required to store the plurality of templates. Furthermore, the time required to do the search will become longer as the number of templates, which have to be taken into account, increases.
Furthermore, in [7], a method for manual edition or correction of a fingerprint minutiae from a displayed fingerprint image is described. The proposed method only deals with one fingerprint. With this method, there is no combination of minutiae, which are obtained from a plurality of fingerprint images, possible.
Furthermore, the least square approach to estimate an inverse of a matrix is described in [8].